1. Field of the Invention
The field of art to which this invention pertains is reactivation of phosphorus-vanadium-oxygen complex catalysts which are used for the production of oxygenated products including aldehydes, ketones, acids and anhydrides.
2. Description of the Prior Art
During normal processing use of phosphorus-vanadium-oxygen complex catalysts for oxidation of hydrocarbons the catalyst becomes deactivated by many separate reactions including formation of coke and in some cases loss of phosphorus. The former can be treated by well-known methods including controlled burning of the coke. In many prior art processes the loss of phosphorus can be compensated by special treatment of the deactivated catalyst including contacting it with organo-phosphorus compounds as illustrated in U.S. Pat. Nos. 3,296,282 (Cl. 260-346.8) and 3.474,041 (Cl. 252-411). Alkyl phosphates have also been used as taught in West German unexamined application (OLS) 2550119 published May 20, 1976, for reactivation purposes.
Other relevant prior art includes U.S. Pat. No. 2,773,921 issued Dec. 11, 1956, having inventors Paul H. Rylander, Jr. and Wilford J. Zimmerschied. This patent was officially classified in Class 260-683.15 and generally relates to a phosphoric acid-vanadium pentoxide catalyst and a hydrocarbon conversion process using such a catalyst.
Other art which may be pertinent includes the use of chlorides or chlorine in maintaining catalyst activity in reforming or other similar processing. In the case of reforming, chloride addition is utilized to maintain a desired chloride level on the catalyst thereby keeping its acidity high enough for sufficient hydrocracking of paraffins.